Self-consistent optical constants of LiF films

Area of Science:

• Materials Science
• Optical Engineering
• Solid State Physics

Background:

• Lithium fluoride (LiF) is crucial for far-ultraviolet (FUV) optics due to its transparency down to 102.5 nm.
• Optical constants of LiF films are temperature-dependent, necessitating accurate characterization.
• Existing data for LiF optical constants, especially for thin films, is limited.

Purpose of the Study:

• To determine self-consistent optical constants for LiF thin films.
• To investigate the temperature sensitivity of LiF film optical properties.
• To provide accurate optical data essential for designing FUV optical elements.

Main Methods:

• LiF thin films were deposited by boat evaporation at 298 K and 503 K.
• In situ reflectance and transmittance were measured from 30-195 nm.
• Ellipsometry was performed from 210-1690 nm and analyzed using Kramers-Kronig (KK) analysis.

Main Results:

• Self-consistent optical constants for LiF films were obtained.
• Calculated optical properties showed good agreement with experimental measurements.
• Novel local sum-rule method confirmed the self-consistency of the optical constants.

Conclusions:

• This study presents the first self-consistent optical constants for LiF films.
• The obtained optical constants are vital for the precise design of FUV optical components.
• The characterization provides critical data for applications in the FUV spectrum.